Insulator



April 17, 1951 H, J, CRABBS 2,549,292

INSULATOR Filed Oct. l2, 1946 Patented Apr. 17, 1951 IN SULATOR Herbert J. Crabbs, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 12, 1946, Serial No. 702,909

This invention relates generally to electric insulators, and more specincally to inserts for such insulators and the manner by which they are anchored in the insulators.

Electric insulators which are made of porcelain, glass or similar materials, require metallic inserts secured thereto in which tapped openings may be provided for the reception of mounting bolts, so that the insulator may be securely mounted on a sup-port or have other devices mounted on the insulator. In the past diiculty has been experienced, p-articularly with insulators of small size, in obtaining adequate mechanical strength in the bond between the insulator and its metallic insert.

IThe general practice is to cement the inserts in openings provided in the insulators. However, the inserts frequently jar loose, especially when an insulator is subject to vibration, due to the low strength of the bond between the cement and metal insert. An adequate bond of the cement to the porcelain may be obtained by incorporating coarse particles of sand in the surface of the 14 Claims. (Cl. 174-206) ing with relatively long insulators because the porcelain during manufacture of the porcelain v lar bond of cement to the insert, coarse sand has also been glazed onto surfaces of the insert. To glaze the insert, however, involves an additional operation, and correspondingly increases the cost of the complete structure.

One object of this invention, therefore, is to provide a novel form of insulator insert which will be capable of forming a high strength bond with cementitious material, without appreciably increasing the cost of the insert.

Another object of this invention is to provide a cast metallic insert for insulators of a novel form capable of forming a high strength bond with cementitious material.

A more specic object of this invention is to provide a novel form of insert having a plurality of integral projections on side surfaces thereof which are adapted to effect a high strength bond with cernentitious material.

Other diiculties `which are encountered in providing inserts for insulators, particularly in the smaller sizes of insulators, are due to the necessity for standardization whereby several factors are fixed, such as the maximum height of the assembled unit, the minimum size and spacing of mounting bolts, the minimum length of tapped openings and these factors must all be met without sacrificing mechanical strength in cantilever, tension, torsion and compression. It is apparent that this problem lmay be readily solved in deal'- inserts can be anchored deep enough in the insulator to obtain the desired strength, but not so with short small insulators.

Accordingly, another object of this invention is to provide a novel form of insulator and insert having provision for maximum length of material bonding surface without materially impairing the mechancal strength of the insulator, especially Where widely spaced tapped openings are required for the insert.

Another object of this invention is to provide an insulator insert having a portion of reduced cross section area adapted to be bonded to an insulator throughout the length thereof, and por-V tions of limited width which extend beyond the area of the first portion in which the insert mounting holes may be tapped.

' These and other objects Y0f this invention will become more apparent upon consideration of the following description of preferred embodiments thereof, when taken in connection with the attac-hed drawing, in which:

Figure 1 is a substantially central longitudinal cross section View taken through an insulator embodying this invention, with the two identical metal inserts beingv shown in elevation and at positions substantially 9G apart relative to the axis of the insulator.

Fig. 2 is a side View partly in central longitudinal section illustrating an insulator and metal insertv assembly comprising a modified form of the invention; and

Fig. 3 is a substantially central longitudinally extending section of still a further modified form 0i the invention, with the metal insulator inserts being shown in elevation.

"In the embodiment of the yinvention shown in Fig. l of the drawing, there is provided an insulator 2 which may be of any desired insulating material, preferably a ceramic material such as porcelain, glass or the like.v Insulator 2 is substantially cylindrical in form, being provided about the periphery thereof with a pair of longitudinally spaced grooves 4, for the purpose of increasing the creepage distance between the ends of the insulator, to increase the voltage at which the insulator may be applied. Opposite ends of insulator 2 are provided with recesses 6 which are substantially identical in form, except that they are adapted tov receive metal inserts which are positioned at substantially an. angle of relative to each other. Each recess 6 is provided with slightly sloping side walls which'are roughened for afpurpose to be described, preferably by imbedding relatively coarse sand in the glaze employed in the case of a porcelain insulator.

In order to mount insulator 2, and to mount electrically conducting parts thereon, metal inserts are provided to be received in the recesses 6, and these inserts are generally required to include tapped openings in which securing bolts may be threadedly mounted. These metal inserts each comprise a substantially cylindrical part 8, which may be slightly tapered as shown in Fig. l, and are preferably of cast metal, such as cast iron, and have a. cross section substantially less than the cross section area of insulator 2, so that the porcelain side walls of recesses 6 will be thick enough to withstand the forces encountered in service. Insulating material, such as porcelain or glass, is relatively brittle and requires a substantial thickness thereof to withstand any appreciable forces.

It will be noted that the metal inserts are each provided with an outer iiange I0 adapted to be seated. on the adjacent outer end of the insulator 2, and they are also provided with an inner flange l2, for a purpose to be described. It will be noted that there is considerable space between the metal insert and the walls of each recess G, and this is for the purpose of receiving a cementitious material which may be poured into this space and hardened around the contours of the metal insert and into the spaces in the roughened side wall of each recess so as to .Form a good bond oi the insulator to the insert. The cementitious material i4 may be either a Portland cement or a cast metal. Each metal insert is also provided with a pair of opposed longitudinally extending ribs I6, and with an intermediate opposed pair of longitudinally extending ribs i8, which are of lesser extent than the ribs l6 Each metal insert is provided with a substantially central tapped opening 20, the length of which is gen- L erally governed by speciiied standards, and this will govern the length of the metal inserts and consequently the depth of recesses 6. The metal 'inserts are also required to have outer tapped openings 22, and the spacing of these openings f,

is also governed by specied standards, and in order to employ an insulator 2 which is of relatively small diameter, integral bosses 24 are provided extending radially from the central portion 8 o each insert which are of length such that the tapped openings 22 may be formed in these portions, and this of course will govern the depth of radial recesses 26 extending from the outer portions of each recess 6 for receiving the bosses 2G, respectively. The radial recesses 26 not only serve to accommodate bosses 24 for tapped openings 22, but they also form effective key portions opposing relative rotation of the metal inserts and insulator 2. Preferably, the bottom of each recess E, and the radial recesses 25 are not roughened or sanded in order to conserve space, and because it has been found that the measures described above and to be described provide ade- Y 28 and 30 are preferably formed integral with the metal insert during the casting process, and this may be accomplished by using a mold which is jammed with molding sand in the usual way around a smooth surfaced pattern. On removal oi the pattern, a large number of depressions may be made in the sand in the area of part 8 of the metal insert by the use of a small blunt instrument or pick, and then a permanent pattern can be made. The purpose of making these depressions parallel is to permit removal of the permanent pattern from the mold. lThe projections 28 and 3) should preferably be relatively long compared to their cross sectional dimensions, and should be` spaced as close together as possible while leaving sufiicient room therebetween for the cementitious material I4 to enter. The projections 28 and 30 are illustrated as being substantially conical in form, and may desirably be formed for one size of insulator about of an inch long, with a maximum diameter of f of an inch, and spaced about 'Se of an inch between centers. In other words, it has been found that a desirable arrangement is to have the projections about twice as long as their maximum cross Sectional dimension, and to have them spaced a distance apart comparable to the length thereof. Projections 28 and 30 should not extend beyond the surface which includes the outer edges of flange l2 and ribs l5 and I8, preferably being of substantially the same extent as these parts.

The inodication of the invention shown in Figs. 2 of the drawing is identical with that shown in Fig. l, except that four bosses 24 are provided adapted to iit in four recesses 26 in insulator 2' so that four outer tapped openings 22 may be provided in the metal insert instead of the two such outer openings illustrated in the construction of Fig. l, and the longitudinally extending ribs I8 are all of the same size. Inasmuch as all other details shown in Fig. 2 are identical with those shown in Fig. 1, a description of these matters will not be repeated in order to avoid unduly lengthening the description of the invention.

The insulator 32, shown in Fig. 3 of the drawing, is somewhat shorter than the insulators shown in Figs. l and 2, but may desirably be made of a similar material and provided with peripheral grooves 34 for the same purpose as grooves 4 in insulator 2. Opposite ends of insulator 34 are provided with recesses 36 which are elongated in form, with the recesses extending in directions substantially 90 apart. The sides of recesses 35 are roughened in a manner similar to recesses E heretofore described, and are adapted to receive a metal insert having a body portion 38 with a general configuration similar to that of the recesses. Each metal insert is provided with an outer ange 4D adapted to set against the adjacent outer end of the insulator, and with an inner flange 42. As in the case of the device shown in Figs. 1 and 2, cementitious material 44 is provided in Fig. 3 for securing the metal insert in its insulator recess, and the portion 38 of the insert may be provided with integral projections 50 which are all substantially parallel, and which may be formed in the same manner as, and of the same size and spacing as the projections 28 and 3Q described above in connection with the devices shown in Figs. l and 2 of the drawing. Ribs 52 may also be provided at each side oi the inserts. The inserts of Fig. 3 each have a relatively large central tapped opening 46, and

outer tapped openings 48 adjacent the outer ends thereof.

It is believed apparent from the foregoing description that the particular insulator constructions disclosed herein -provide for a relatively high mechanical strength resistance as to forces applied to the insulator inserts. This is accomplished by the provision of means comprising the roughened side wall of the insulator recesses and the integral projections provided on the metal inserts, which extend substantially throughout the entire length of the recesses and inserts for providing a good bond of the cementitious material to the insulator and to the insert itself. This feature provides an unusual resistance to vibration, preventing the inserts from working loose. As previously stated, torsional forces are resisted by the integral bosses 24 in the case of the species of invention shown in Figs. 1 and 2, and by the elongated form of the insert and recess in the case of the device shown in Fig. 3. Adequate resistance to tension forces are provided not only by the roughened surfaces of the insulator recesses and the integral projections on the metal inserts, but also by the inner flanges on the inserts to securely anchor them against such tensile forces. In addition to providing adequate inechanical strength by reason of the features pointed out above, all this is accomplished with a smaller size of insulator than had heretofore been employedby reason of the particular form of the metal inserts and insulator recesses accommodating the outer tapped openings in the inserts. With the particular constructions described above, the outer tapped openings of the insert may be located closely adjacent the outer edge of the insulator itself and yet provide for much greater thickness of insulating material than that between the tapped opening and outside of the insulator, which larger area (that located between the bosses, and at the sides of the insert shown in Fig. 3) is entirely adequate to resist breakage from forces encountered in service.

Having described preferred embodiments of the inventionin accordance with the patent statutes, it is desired that this invention be not limited to these particular constructions, inasmuch as it will be apparent especially to persons skilled in the art that many modifications and changes may be made in these particular constructions without departing from the broad spirit and scope of this invention` Accordingly, it is desired that the inventionbe interpreted as broadly as possible, and that it lbe limited only as required by the prior art.

I claim as my invention:

1. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, at least longitudinally extending portions of the confronting surfaces of said recess and insert portion for substantially the entire lengthl thereof having means thereon to interlock in all directions with cementitious material interposed between said surfaces, and said insulator and insert also having a plurality of spaced integral radially extending interlitting projection and recess means located on other longitudinally` extending portions of said surfaces.

2. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted tof be secured in said recess, at least longitudinally extending portions of the lil) confronting surfaces of said recess and insert portion for substantially the entire length thereof having a plurality of closely spaced irregularities to interlock in all directions with cementitious material interposed between said surfaces, and said insulator and insert also having a plurality of spaced integral radially extending inte-rfitting projection and recess means located on other longitudinally extending portions of said surfaces.

3. In an insulator, a vbody of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, at least longitudinally extending portions of the confronting surfaces of said recess and insert portion for substantially the entire length thereof having means thereon to interlock in all directions with cementitious material interposed between said surfaces, said insulator and insert also having a plurality of spaced integral radially extending intertting projection and recess means located on other longitudinally extending portions of said surfaces, and said projection and recess means being devoid of interlocking means,

4. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, at least longitudinally extending portions of the confronting surfaces of said recess and insert portion forsubstantially the entire length thereof having means thereon to interlock in all directions with cementitious material interposed between said surfaces, and spaced laterally extending projections on said insert portion which are received in corresponding recesses in said insulator and located at other longitudinally extending portions of said surfaces.

5. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, at least longitudinally extending portions of the confronting surfaces of said recess and insert portion for substantially the entire length thereof having means thereon to interlock in'all directions with cementitious material interposed between said surfaces, spaced laterally extending projections on said insert portion which are re-I ceived in corresponding recesses in said insulator and located at other longitudinally extending portions of said surfaces, said projections and recesses being adjacent the outer end of said first-mentioned recess, and tapped openings at the outer end of said insert formed inthe material thereof forming said projections.

projection and recess means located on other' longitudinally extending portions of said surfaces.

7. In an insulator, a body of insulating material having a recess therein, a cast-metal insert having a portion adapted to be received in said recess, at least longitudinally extending portions of the confronting surfaces of said recess and insert portion for substantially the entire length thereof having irregularities comprising a plurality of longitudinally and circumferentally spaced integral parallelly extending projections on said insert portion to interlock with cementitious material interposed between said surfaces, and said insulator and insert also having spaced integral radially extending interitting projection and recess means located on other longitudinally extending portions of said surfaces.

8. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, spaced laterally extending projections at the upper end of said insert which are received in corresponding recesses in said insulator, tapped openings in said projections, and substantially all of the remaining confronting surfaces of the iirst mentioned recess and insert having means thereon to interlock in all directions with cementitious material interposed between such remaining surfaces.

9. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, spaced laterally extending projections at the upper' end of said insert which are received in corresponding recesses in said insulator, and tapped openings in said projections.

10. In an insulator, a body of insulating material having a recess therein, a metal insert having a portion adapted to be secured in said recess, a

flange on the outer end of said insert, spaced laterally extending projections on said insert integral therewith and with said ange and being of substantially the same lateral extent as said flange, and tapped openings in said ange which extend into said projections.

l1. An insulator comprising, a body of insulating material having a recess in each end thereof, metal inserts each having a portion secured in the respective ones of said recesses, opposed laterally extending projections at the outer end of each of said inserts which are received in corresponding recesses in said insulator with the projections of the two inserts being out of registry, and tapped openings in said projections.

12. An insulator comprising, a body, of insulating material having a recess therein, a castmetal insert having a portion adapted to be received in said recess, cementitious material nlling the space between the walls of said recess and insert, and a vibration resistant bond between said insert and cementitious material comprising, a relatively large number of uniform integral projections on said insert, each of said projections being of a length materially greater than its maximum cross sectional dimension and said projections being uniformly spaced from each other in all directions to permit said cementitious material to entirely surround each projection.

13. An insulator comprising, a body of insulating material having a recess therein, a castmetal insert having a portion adapted to be received in said recess, cementitious material filling the space between the walls of said recess and insert, and a vibration resistant bond between said insert and cementitious material comprising, a relatively large number of uniform, parallel, and outwardly tapered integral projections on said insert, each of said projections being of a length materially greater than its maximum cross sectional dimension and said projections being uniformly spaced from each other in all directions to permit said cementitious material to entirely surround each projection.

14. An insulator comprising, a body of insulating material having a recess therein, a castmetal insert having a portion adapted to be received in said recess, cementitious material filling the space between the walls of said recess and insert, and a Vibration resistant bond between said insert and cementitious material comprising a relatively large number of uniform, conical, integral projections on said insert, each of said projections being of a length materially greater than its maximum cross sectional dimension and said projections being uniformly spaced from each other in all directions to permit said cementitious material to entirely surround each projection.

HERBERT J. CRABBS.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 678,195 Potter July 9, 1901 1,257,516 Muckey Feb. 26, 1918 1,284,975 Austin Nov. 19, 1918 1,376,486 Von Kando May 3, 1921 1,500,626 Kyle July 8, 1924 1,950,646 Austin Mar. 13, 1934 1,958,435 Hawley May 15, 1934 1,961,402 Taylor June 5, 1934 1,981,717 Austin Nov. 20, 1934 2,376,761 Fahy May 22, 1945 

